The present invention generally pertains to assembly toys and is particularly directed to an improved building element for a set of toy building blocks.
Referring to FIGS. 1A and 1B, one type of prior art building element for a set of toy building blocks that has been popular for many years comprises a box 10 having a top 11, a bottom 12 and side walls 13, wherein the top 11 of the box 10 includes a two-dimensional array of cylindrical projections 14 and the bottom 12 of the box 10 is open. The interior surfaces 15 of the box 10 and an interior tube 16 are accessible through the bottom 12 of the box 10 for interconnecting with one or more of the projections 14 on the top 11 of another such building element in a releasable frictional engagement. The side walls 13 of this type of building element do not include any means for directly coupling a side wall 13 of the building element to a side wall 13 of another such building element.
Another type of prior art building element for a set of toy building blocks, as shown in FIGS. 2A and 2B, comprises a box 20 having a top 21 including a cylindrical projection 22; a bottom 23 which is open to expose interior surfaces 24 that are accessible for interconnecting with the projection 22 on the top 21 of another such building element in a releasable frictional engagement; and side walls 25, 26 that include means for directly coupling a side wall 25, 26 of the building element to a side wall 26, 25 of another such building element. Each of a pair of side walls 25 on opposite sides of the box 10 include a groove 27 having an entry opening of a given predominant width w.sub.g and the other two side walls 26 include a projection in the shape of a tongue 28 having a distal portion of a predominant width w.sub.t that is greater than the given predominant width w.sub.g of the groove entry opening for interconnecting in a releasable restraining engagement with a groove 27 in another such building element. The tongue 28 can be engaged with and disengaged from the groove 27 in the other such building element by sliding the tongue 28 into or from one end of the groove 27 in the other building element. Also, the building element is made of plastic material having sufficient flexibility that the tongue 28 can be engaged with the groove 27 in the other such building element by frontally pressing the tongue 28 into the groove 27 and can be disengaged therefrom by either twisting or frontally pulling the building element from the other such building element. Based upon experience in interconnecting and disconnecting this type of building element, it seems that at least as much force is required to engage a tongue 28 into a groove 27 when frontally pressing the tongue 28 into the groove 27 as is required to disengage the tongue 28 from the groove 27 by frontally pulling the building element from the other said building element. This type of building element is further described in International Patent Application Publication No. WO 93/04749.